Superconducting materials have been applied epitaxially to biaxially textured support materials in the ongoing effort to fabricate robust, flexible superconductors characterized by sufficiently high high critical current density (Jc) and scalability to industrially useful lengths. An important class of substrates is known as rolling assisted, biaxially textured substrates (RABiTS). The present invention is an important stepping stone in that effort.
Biaxial texture refers to {100}<100> crystallographic orientations both parallel and perpendicular to the basal plane of a material. A material having biaxial texture of sufficient quality for superconductor applications can be generally defined as being characterized by an x-ray diffraction phi scan peak of no more than 20° FWHM. Other suitable definitions have also been set forth in varying terms. For the purpose of the description of the present invention, biaxial texture is construed to include single-crystal morphology.
It is helpful to review some of the prior work that the present invention builds upon. The entire disclosure of each of the following U.S. patents is incorporated herein by reference:
U.S. Pat. No. 5,739,086 issued on Apr. 14, 1998 to Goyal, et al.
U.S. Pat. No. 5,964,966 issued on Oct. 12, 1999 to Goyal, et al.
U.S. Pat. No. 5,968,877 issued on Oct. 19, 1999 to Budai, et al.
U.S. Pat. No. 5,972,847 issued on Oct. 26, 1999 to Feenstra, et al.
U.S. Pat. No. 6,077,344 issued on Jun. 20, 2000 to Shoup, et al.
U.S. Pat. No. 6,114,287 issued on Sep. 5, 2000 to Lee, et al.
U.S. Pat. No. 6,150,034 issued on Nov. 21, 2000 to Paranthaman, et al.
U.S. Pat. No. 6,159,610 issued on Dec. 12, 2000 to Paranthaman, et al.
U.S. Pat. No. 6,180,570 issued on Jan. 30, 2001 to Goyal.
U.S. Pat. No. 6,256,521 issued on Jul. 3, 2001 to Lee, et al.
U.S. Pat. No. 6,261,704 issued on Jul. 17, 2001 to Paranthaman, et al.
U.S. Pat. No. 6,270,908 issued on Aug. 7, 2001 to Williams, et al.
U.S. Pat. No. 6,331,199 issued on Dec. 18, 2001 to Goyal, et al.
U.S. Pat. No. 6,440,211 issued on Aug. 27, 2002 to Beach, et al.
U.S. Pat. No. 6,447,714 issued on Sep. 10, 2002 to Goyal, et al.
U.S. Pat. No. 6,451,450 issued on Sep. 17, 2002 to Goyal, et al.
U.S. Pat. No. 6,617,283 issued on Sep. 9, 2003 to Paranthaman, et al.
U.S. Pat. No. 6,645,313 issued on Nov. 11, 2003 to Goyal, et al.
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U.S. Patent Application Publication No. 20030143438 published on Jul. 31, 2003 to Norton, et al.
U.S. patent application Ser. No. 10/324,883 filed on Dec. 19, 2002.
U.S. patent application Ser. No. 10/620,251 filed on Jul. 14, 2003.
Moreover, there are other known routes to flexible electromagnetic devices known as ion-beam-assisted deposition (IBAD) and inclined-substrate deposition (ISD). IBAD processes are described in U.S. Pat. Nos. 6,632,539, 6,214,772, 5,650,378, 5,872,080, 5,432,151 and 6,361,598; ISD processes are described in U.S. Pat. Nos. 6,190,752 and 6,265,353; all these patents are incorporated herein by reference.
Some of the problems that have been encountered are substrate and/or buffer layer oxidation, diffusion of substrate components into the other buffers and/or superconductors, and instability (e.g., thermal runaway) of the superconductors during an over-current situation. For example, the use of Cu substrates would be desirable because they would enable reduced ferromagnetism, higher electrical conductivity, higher heat capacity, and lower cost compared with Ni and Ni alloys. However, Cu is particularly susceptible to problems such as those mentioned above.